In response to the Funding Opportunity Announcement "Development of Assays for High-Throughput Drug Screening," we propose here to develop assays to identify and analyze inhibitors of helicases needed for RNA virus replication. All viruses require helicases to separate duplex DNA or RNA, yet helicases remain undeveloped antiviral drug targets. Although some helicase inhibitors that target DNA viruses are progressing in clinical trials, no antiviral agents targeting RNA viruses have entered the clinical arena. We therefore will target RNA viruses, focusing on pathogens with abnormally high global burdens of disease: hepatitis C virus (HCV), Dengue virus (DENV), West Nile virus (WNV), Japanese encephalitis virus (JEV), yellow fever virus (YFV), and human immunodeficiency virus (HIV). The assays to be developed are needed as part of an ongoing collaborative hypothesis-driven research project to develop HCV NS3 helicase inhibitors as chemical probes to facilitate basic science and for drug development. In that endeavor, we have initiated an uHTS at the MLPCN that uses our recently developed molecular beacon based helicase assay (MBHA) as a primary screen. To evaluate HCV helicase inhibitor specificity, MBHAs will be developed using helicases encoded by viruses related to HCV (DNV, WNV, YFV, and JEV) and human cellular helicases. The human proteins to be analyzed have all been linked to HIV replication and include the DEAD-box proteins DDX1, DDX3, DDX24, MDA-5, RNA helicase A (RHA), and Werner syndrome protein (WRN). In aim 2, assays will be developed to analyze the cellular antiviral efficacy, and mechanism of action of HCV helicase inhibitors. Mechanistic assays include ATPase assays, ligand binding assays, protein oligomerization assays, and simultaneous protease/helicase assays. Most of these mechanistic assays could be used with either HCV helicase or one of the ten other helicases targeted here to screen for additional classes of helicase inhibitors. PUBLIC HEALTH RELEVANCE: In collaboration with a NIH high throughput-screening center, my lab is searching a collection of hundreds of thousands of small molecules for compounds that might inhibit the helicase encoded by the hepatitis C virus (HCV). In this project, we will develop tests to rapidly search these HCV helicase inhibitors for compounds that could be used to treat hepatitis C. We will also develop similar assays to identify compounds that might inhibit viruses that cause AIDS, yellow fever, Dengue fever, West Nile and Japanese encephalitis.